Chapter C5 Chemical changes (C5.2 Displacement reactions (Hydrogen and…
Chapter C5 Chemical changes
C5.3 Extracting metals
Where do metals come from?
Metals are found in the Earth crust, they are combined with other chemical elements, mostly with oxygen and sulfur.
They are found in the rock called a metal ore. They are mined from the ground, some specific metals need to be extracted and purified, some metals such as gold and silver are very unreactive and they are found Earth as a metal themself.
C5.2 Displacement reactions
Hydrogen and carbon in the reactivity series
In reactive series, the more reactive metal will displace a less reactive metals
Copper cannot displace the hydrogen from an acid, therefore hydrogen is positioned between copper and lead.
Carbon can only extract metal from their oxides that are below aluminium in the reactivity series.
Oxidation and Reduction
Oxidation is the loss of electrons whereas Reduction is the gain of electrons
Oxidising give oxygen to another substance. Reducing remove oxygen from another substance.
C5.1 The reactivity series
Metals plus water
Metals such as copper don't react at all with water, however, potassium plus water is the most reactive.
Magnesium is between lithium and copper in the reacitivity series, which takes time to collect enough hydrogen to test with a lighted spill, there will be a pop sound.
Metals plus dilute acids
potassium, sodium, lithium and calcium is really explosive when its react with diulte acids.
magnesium, aluminium, zinc and iron, when react with dilute acid its fizzes, abd giving off hydrogen and form a salt.
C5.5 Salts from insoluble bases
Formulae of salt
acid + base = salt + water
Salt are formed by positive metal ions and negative ion from acid, and salts have no overall charge, because add the ions together is equal to zero
Add copper oxide to sulphuric acid and gently stir
When the solutions turns blue, it means that copper sulfate is formed.
When the reaction is complete, use filter paper to remove excess copper oxide.
Start heating it till you see one crystal, then turn off bunsen burner and leave it to evaporate in room temperature.
C5.4 Salts from metals
Acid, metal, salt
Reactions between a metals and acid can onlu be available when the metal is more reactive than the hydrogen according to reactivity series.
When reactions take place. there will bea salt formed, because hydrgen and acid is wholly. replaced by metal ions.
The best way to have a good samples of salt crystals, is that the after heating it up, leave at room temperature so that the water evaporate slowly.
Metal with acid is always a redox reaction, because the metal atoms will give electrons to the hydrogen ions, which displace hydrogen and leave the metal ions in the solution.
C5.6 Making more salts
acid + alkali
Neutralisation take place when an acid reacts with an alkali
When react with acid and alkali, there will be no gas given off during the reaction, so you cant tell whether or not the acid and alkali have completely reacted
So the only way to know is to use acid indicator to help decide when the reaction is complete by the colour.
C5.7 Neutralisation and the pH scale
Alkalis is soluble hydroxides, one of the example is sodium hydroxide solution
Bases is with alkalis that can neutralise acids, for example, metal oxides and metal hydroxides are bases
Acids taste very sour, but some acid is really dangerous to put in your mouth
Measuring acidity or alkalinity
Indicators change colour depending on the acids and alkalis of the concentration
It turns a range of colours due to pH changes, in the middle pH7 is neutral, it is not acidic and alkaline.
Acids are substance that produce H+ ions when you add them to water.
Alkali is a soluble hydroxide that produce OH- ions when add it to water.